Rice cultivar variability in tolerance for accelerated aging of seed

Treated seed and seed from a nonteated control were tested for germination at 25-30 C. A portion of the seed of each of 30 selected cultivars from the WS cropping was treated with dry heat at 50 C for 5 d to break dormancy, the remaining portion serving as an untreated (dormant) control. Both treated seed and the untreated seed were subjected to accelerated aging treatments for 2, 4, and 6 d and their germinations compared. Cultivars with superior tolerance for the aging conditions were found in each of the ecogeographic races of Oryza sativa L. (incica, japonica, and javanica) and among photoperiod-sensitive and insensitive strains, upland and lowland types, and salt-tolerant and tungro virus-resistant cultivars. In general, the higher the dormancy level of the seed, the greater was the tolerance for accelerated aging. (Author abstract)